Issue: SPR-14971
(cherry picked from commit aef1460a)

Issue: SPR-15005
(cherry picked from commit 8b5ee4ef)

This commit also migrates from a WeakHashMap to a ConcurrentReferenceHashMap, allowing for concurrent access to existing cache entries.

Issue: SPR-15006
(cherry picked from commit b825528d)

Issue: SPR-14996
(cherry picked from commit 547b9638)

CommonsMultipartFile.getOriginalFilename() can be configured to preserve header-specified filename as-is

Issue: SPR-14613
(cherry picked from commit aa29495d)

Issue: SPR-14940
(cherry picked from commit 52799c0e)

Issue: SPR-14994
(cherry picked from commit 953bc189)

Issue:  SPR-14986
(cherry picked from commit 7714eecc)

Issue: SPR-14972
(cherry picked from commit a7ec6dc0)

Issue: SPR-14990
(cherry picked from commit 278a6250)

Issue: SPR-14985
(cherry picked from commit ee30ce95)

Issue: SPR-14976
(cherry picked from commit 8ab977e7)

Issue: SPR-14957
(cherry picked from commit 2f80b848)

Issue: SPR-14361
Issue: SPR-14987
(cherry picked from commit 05579fd1)

Issue: SPR-14969
(cherry picked from commit 6517c537)

Previously ForwrdedHeaderFilter did not ensure that
HttpServletResponse.sendRedirect worked properly based on
X-Forwarded-* headers.

This commit updates ForwardedHeaderFilter to overrided the
HttpServletResponse.sendRedirect method to ensure
X-Forwarded-* headers are honored.

Issue SPR-15020

This commit makes it possible for a ChannelInterceptor to override the
user header in a Spring Message that contains a STOMP CONNECT frame.

After the message is sent, the updated user header is observed and
saved to be associated with session thereafter.

Issue: SPR-14690

Issue: SPR-14995

The `pathPatterns` args are relative to the patterns configured for the
resource handler.

Issue: SPR-14817
Cherry-picked from: 52f66413

When getting the lookup path of a resource, both query params and hashes
should be removed from the request path.

This commit fixes the public path resolution for paths like
`/resources/main.svg#icon-hamburgermenu`.

Issue: SPR-14928

Prior to this commit, `@ExceptionHandler` methods could not be injected
with `RedirectAttributes` arguments. This would make it impossible to
handle an error by redirecting to another view and add flashmap
attributes, to be included in the model when the next view is called.

Here is an example:

```
@ExceptionHandler(MyException.class)
public String handleException(MyException ex, RedirectAttributes
    redirectAttributes) {

  redirectAttributes.addFlashAttribute("errorMessage",
      "This is an error message");
  return "redirect:/";
}
```

This commit adds a new `RedirectAttributesMethodArgumentResolver`
instance in the list of pre-configured `HandlerMethodArgumentResolver`
in `ExceptionHandlerExceptionResolver`.

Issue: SPR-14651
Cherry-picked from: 17089d60

Due to a few changes in `WebSocketServerFactory` and `Session` API, our
`JettyRequestUpgradeStrategy` and `JettyWebSocketSession` needed to
adapt. As of 9.3.15+ and 9.4.0+, some reflection is required to support
previous versions.

Spring 4.3 websocket officially supports Jetty 9.1 to 9.3.

Issue: SPR-14940

This reverts commit 305cea28.

Due to a few changes in `WebSocketServerFactory` and `Session` API, our
`JettyRequestUpgradeStrategy` and `JettyWebSocketSession` needed to
adapt. As of 9.3.15+ and 9.4.0+, some reflection is required to support
previous versions.

Spring 4.3 officially supports Jetty 9.1 to 9.3.

Issue: SPR-14940

Issue: SPR-14901

Issue: SPR-14899

Issue: SPR-14988

This commit ensures that POST/PUT requests sent by the Netty client have
a Content-Length header set.

Integration tests have been refactored to use mockwebserver instead of
Jetty and have been parameterized to run on all available supported
clients.

Issue: SPR-14860
Cherry-picked from: ec8391a7

Latest dependency updates (Caffeine 2.3.5, Hibernate ORM 5.2.5, Joda-Time 2.9.6, Tomcat 8.5.8, JOpt Simple 5.0.3)

Issue: SPR-14958

PathMatchingResourcePatternResolver converts manifest entries to absolute paths and tries all root URLs (any file extension) as jar file

Issue: SPR-14934
Issue: SPR-14936

Issue: SPR-14969
(cherry picked from commit 7a8ec4f6)

Issue: SPR-14960
(cherry picked from commit 845dbf04)

Issue: SPR-14958
(cherry picked from commit 1ae17c27)

Issue: SPR-12889
(cherry picked from commit 01868096)

Issue: SPR-14926
Issue: SPR-12926
(cherry picked from commit f6b8b84d)

* getBeanDefinitionNames defensively returns a copy of the bean definition names array.
* copyConfigurationFrom provides an independent AutowireCandidateResolver instance and copies a ConversionService and dependency comparator configuration as well.
* findAutowireCandidates only considers a self reference fallback for direct dependency declarations, not as a collection element.

Issue: SPR-14897
Issue: SPR-14921
Issue: SPR-14965
(cherry picked from commit ac5933a7)